1. Field of the Invention
This invention relates to a metallized colored transparent thermoplastic laminated film for use alone or in thermoformed trays.
2. Brief Description of Related Art
Metallized sheet or films for thermoformed trays consisting of a layer of thermoplastic sheet or film that has been metallized by a vacuum process to provide a metallized sheet or film is well-known. Metallized plastic articles may be prepared by applying a metal to a plastic material by vacuum deposition, electrolytic deposition, foil lamination or similar metallizing techniques. Such articles are widely employed for decorative purposes, particularly the metallized films which are quite flexible and can be shaped to some extent to conform to various contours.
U.S. Pat. No. 4,528,234 describes a transparent laminate. The laminate has a transparent plastic resin film or sheet substrate that has a thin metal layer formed on one side. A carboxyle group containing polyolefin layer is formed on the metal layer by lamination.
U.S. Pat. No. 4,825,025 describes a food receptacle for microwave cooking. The receptacle generally has three layers. The uppermost layer is a high heat tolerant protective layer, which ensures that the food product does not touch the metal layer or the substrate. Underneath the uppermost layer is a thin layer of a conductive material. These two layers are mounted on a substrate, preferably paper.
U.S. Pat. No. 5,106,670 describes a metallized package component. The component includes at least two layers of a thermoplastic polymeric laminate, which may be bonded together by an adhesive. A metallic layer is disposed on the top surface of the laminate and is visible from both sides of the laminate.
U.S. Pat. No. 4,360,551 describes a flexible film laminate. The laminate has a first layer of a heat-sealable polyolefin, a second layer of a previously metallized thermoplastic polymer that is bonded to the first layer, and an adhesive for bonding the metallized surface of the second layer to the first layer.
U.S. Pat. No. 4,308,084 describes a laminate for packaging foodstuffs. The laminate has an aluminum substrate. The substrate is laminated to a polyolefin film using a polyolefin resin as an adhesive.
U.S. Pat. No. 4,211,822 describes highly reflective multilayer metal and polymer composites. The composite has a thermoplastic polymer outer layer, one side of which is intimately bonded with a layer of a soft metal. The composite is then formed by a conventional forming process to the desired shape.
U.S. Pat. No. 4,936,935 describes a microwave heating material. A metal layer is bonded to a substrate layer, which is then overlaid with an outer lacquer layer. The substrate may be a polymer.
U.S. Pat. No. 5,834,046 describes a closure for microwave cooking. The bottom portion of the closure is a lamination. A moisture barrier polyolefin is laminated to a thermoformable substrate, which is typically a polyester.
However, metallized sheet or film has certain disadvantages and limitations. While the metallized layer is located on the bottom of the sheet and not in direct contact with the food product that will be packaged in a tray formed from this sheet, the top of sheet may nevertheless contain particles of metal due to these having rubbed off during the nesting of the trays. Such particles can contaminate the product package on the tray. Additionally, from time to time for different reasons moisture may come into contact with the metallized particles causing the color to change from a shiny bright look to a dirty rusty aspect.
U.S. Pat. No. 4,559,266 describes laminated materials for thermoforming into food packaging. The laminate has a layer of mainly polyolefin, a layer of a polymer, a metal-vacuum deposited layer and a layer of a transparent thermoplastic material.
However, the present metallized sheets provide a bright shiny look such as gold or silver on one side only rather than on both. Thus there is still a need to provide a metallized color effects (either of the same aspect or of different aspects) from both sides of the film.
It is therefore a principal object of the invention to overcome the shortcomings of the devices heretofore mentioned.
It is a further object to provide colored metallized film and trays.
It is a further object to provide film and trays with metallized colors.
It is a further object to provide film and trays having two sides each with different metallized colors.
It is an object to provide metallized film and trays which do not rub off metal particles upon contact.
It is a further object provide metallized film and trays which do not rust.
The invention is a multilayer laminate. To solve the above problems, a new thermoplastic sheet or film has been developed comprising a base layer of a transparent colored layer, made of styrenic films such as OPS (oriented polystyrene) polyester films such as PET (polyethylene terephthalate), polyolefin films such as polypropylene, polyethylene, PVCs (polyvinyl chlorides) or similar film materials. The base layer is then metallized by a vacuum process to provide a metallized sheet or film. A second thermoplastic sheet or film is then laminated over the metallized layer. The laminating sheet or film is transparent and may be either clear or have a desired color. If a colored laminated layer is selected then a different color is seen on each side of the sheet. The sheet may then be converted into a thermoformed tray.
Accordingly, by laminating a sheet or film (of any of the above indicated categories) over a previously metallized sheet or film, two of the existing problems presently encountered are solved, namely metal particles rubbing off on food and the rusting of the metal trays themselves. Furthermore, the invention provides the commercially desirable possibility of a new combination of metallized colors, heretofore not available at reasonable costs. Additionally, the new type of sheet may be converted into thermoformed trays in preferred embodiments of the invention.